1. Field of the Invention
The invention relates generally to optical viewfinders for autofocus cameras, and in particular to a viewfinder having an autofocus frame for framing the focus subject, i.e., the main subject the photographer wishes to focus on, in the picture to be taken. More specifically, the invention relates to electrically activated indicator means for highlighting the autofocus frame to prominently call attention to whether or not the focus subject is within the autofocus frame before the picture is taken.
2. Description of the Prior Art
Automatic focusing is one feature which was long neglected in the development of camera automation. However, the introduction of an autofocus module in a 35 mm camera several years ago has brought a large number of inexpensive autofocus cameras into the market. In these cameras, the focusing distance, i.e., the camera-to-subject distance at which the taking lens will be in focus, is automatically measured and the taking lens is driven to a focused position in accordance with the measured distance.
One recent example of an inexpensive rangefinder type 35 mm autofocus camera, namely the Ricoh FF-3AF, is operated as follows:
1. The scene is composed in a projected reticle viewfinder with the focus subject located within an autofocus frame at the center of the viewfinder.
2. The shutter release button is depressed approximately halfway until either a near zone symbol or a far zone symbol lights up in the viewfinder to indicate that the focusing distance has been set within a near or far zone. The distance data is inputted to a focus memory, and can only be cancelled by releasing the shutter release button. If the near mark blinks, the camera is too close to the main subject for the focus distance to be set and should be moved back a little.
3. The shutter release button is depressed fully, which initiates movement of the taking lens to a focus position derived from the distance data in the focus memory, and the picture is taken.
If you want to photograph two (or more) people using the Ricoh camera or other similarly operated cameras, there may be instances where both of the people cannot be located within the autofocus frame in the viewfinder. If you release the shutter then, only the background will be in focus and the people which are the main subject will be out of focus. Accordingly, with the Ricoh camera, a prefocus procedure is recommended, as follows:
1. Move the camera so that only one of the people is located within the autofocus frame. PA1 2. Depress the shutter release button halfway to set the focusing distance. PA1 3. Holding your finger in that position on the shutter release button, return the camera to its former position so that both of the people are centered in the viewfinder again. PA1 4. Depress the shutter release button fully to take a picture.
This procedure also applies to situations where you want the main subject you wish to focus on to be located off-center in the viewfinder when the picture is taken.
In many of the recently introduced rangefinder type autofocus cameras, the autofocus frame is only faintly visible in the projected reticle viewfinder, especially in a moderately lit or dim light situation. Consequently, the autofocus frame does not prominently call attention to the area of the picture that the autofocus system is ranging on to set the focusing distance. Thus, when the main subject you wish to photograph is outside the autofocus frame, you may forget to use the pre-focus procedure described above. As a result, the autofocus system will focus on the background so that the main subject will be out of focus.